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Name…………………………………………Index No…………………………………………..

Class……………………...Candidate’s Signature.........................................................................

CHEMISTRY 233/2 FORM 4 PAPER2 TIME: 2 HOURS Instructions to Candidates

1. Answer ALL the questions in the spaces provided

2. Mathematical tables and silent electronic calculators may be used.

3. All working must be clearly shown where necessary.

For Examiner’s Only.

This paper consists of 15 printed pages. Candidates should check the question paper to ensure that all pages are printed as indicated and no questions are missing.

Question Maximum Candidate’s 1. 12 2. 12 3. 10 4. 12 5. 14 6. 11 7. 9

80 Total score

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1. The chart is a part of the periodic table. Study it and answer the questions that follow.

A B C D E F G H J a) i) Select the element in the period 3 that has the smallest atomatic radius. Give a reason for

your answer. (2marks)

……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………....

ii) Write the chemical formula of a compound between element D and J (1 mark)

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iii) Explain why the melting point of element J is higher that of G. (2marks)

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iv) What type of structure will the chloride of element E have? (1mark)

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v) State one use of element C (1mark)

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vii) Element G reacts more vigorously with hot iron than element J. Explain? (2marks)

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b) What 3 litres of chloride gas were completely reacted with element, 10.0g of the product were formed. Determine the relative atomic mass of element A.

(Atomic mass of chlorine =35.5, Molar Gas Volume is 24 Litres). (2marks)

……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………........................

2. a) The diagram below represents fractional distillation of liquid Air.

The boiling points of oxygen, orgon and nitrogen are -1830, 1860C and -1930C respectively.

i) Identify gas A:…………………………………………………………. (1mark)

B:…………………………………………………………. (1mark)

ii) State whey gas B is collected at the lower end of the fractionating column (1mark)

……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………...

LIQUID AIR

NITROGEN

GAS A

GAS B

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iii) b) The set up below is used to prepare oxygen

i) Name solid A (1mark)

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ii) State the function of solid D (1mark)

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iii) Write an equation for the reaction that occurs in the round-bottomed flask (1mark)

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iv) Give two reasons why oxygen is collected as shown (2marks)

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v) Hot potassium metal was placed in a gas jar containing oxygen. State two observations made (2marks)

OXYGEN

WATER SOLUTION D

HYDROGEN PEROXIDE

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………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

vi) Give two uses of oxygen (2marks)

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3. In an experiment to determine water of crystallization in a commercial washing soda

• Na2CO3.XH2O, a student was provided with;

• -Na2CO3XH2O Solution D containing 14.3g per litre of solution

• Hydrochloric acid solution K containing 7.3g per litre of solution

She pipette 25cm3 of solution D into 250ml conical flask, then added 3 drops of phenolphthalein indicator and titrated using solution K and a burette.

She recorded her results in the table below.

Titration 1 2 3 Final Burette reading (cm3) 12.4 24.8 24.8 Initial burette reading (cm3) 0.0 12.40 37.2 Titre (cm3) 12.4 12.4 12.4

a) Identify two mistakes from her table (2marks)

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b) Calculate the average volume of the acid D used (1mark)

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c) Write a balanced equation for the reaction between D and K (1mark)

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………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

d) Calculate the number of moles of hydrochloric acid K that reacted (1mark)

(H=I, CL=35.5)

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

e) Calculate the number of moles in 25cm3 of solution D (1mark)

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f) (i) Calculate the relative molecular mass of the washing soda (2marks)

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(ii) Hence determine the value of X (1mark)

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4. a) A student assembled apparatus as shown below to prepare sulphure (IV) oxide gas in the laboratory. Study the diagram then answer the questions below.

i) Complete and label the diagram to show how dry sulphure (IV) oxide gas is produced and collected (21/2 marks)

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ii) By use of a chemical equation, explain why fused calcium oxide is not a suitable drying agent for SO2 (2marks)

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

SOLUTION L

Concentrated sulphuric acid

Sodium sulphite

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b) Sulphuric (VI) Acid is an important industrial reagent. It is manufactured by the contact

process represented by the flow diagram below.

i) Identify the substance

Solid A (11/2marks)

…………………………………………………………………………………………..

Gas X (11/2marks)

………………………………………………………………………………………….

Gas Y (11/2marks)

………………………………………………………………………………………….

ii) State the importance of

The cleaner (1mark)

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The drier (1mark)

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iii)Write an equation for the reaction that takes place in the dilution chamber (1mark)

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iv) On the diagram above, draw a line that represents recycling of SO2 (1mark)

v) Other than vanadium (V) oxide, state another catalyst that can be used in the catalytic chamber. Why is this catalyst not commonly used? (2marks)

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vi) State one use of sulphuric (VI) acid. (1mark)

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5. A student carried out an experiment to determine the molar enthalpy of neutralization of sodium hydroxide by 2M hydrochloric acid. 25cm3 of the acid was placed in a beaker and the initial temperature of the solution measured and recorded. 5cm3 of sodium hydroxide was added to the beaker and the mixture temperature recorded. The procedure was repeated and the temperature recorded as in the table below.

Volume of acid (cm3) 25 25 25 25 25 25 25 Volume of NaOH added (cm3)

0 5 10 15 20 25 30

Temp(0C) of solution 28.0 31.0 34.0 37.0 40.0 39.0 37.0

a) On the grid provided, plot a graph of temperature against volume of sodium hydroxide added. (3marks)

b) From the graph, determine:

i. The maximum expected temperature change ∆T (1mark)

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

ii. The volume of sodium hydroxide required to neutralize the hydrochloric acid(1mark)

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………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

c) Calculate the heat change that occurred during the reaction (C=4.2kJ1K-1, assume density of solution = 1g/cm3) (1 mark)

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d) Find the number of moles of sodium hydroxide that reacted (1mark)

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e) Determine the molar enthalpy of neutralization for this reaction (1mark)

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

f) Suggest a reason why the above value in (e) could be lower than the actual value (1mark)

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g) (i) Give two points to be considered when choosing a fuel (2marks)

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(ii) Give one precautions necessary when using a charcoal stove (1mark)

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6. Study the flow chart below and use it to answer the questions that follow.

a) Write the name of the processes shown

I …………………………………………………………………………………(1mark)

II ………………………………………………………………………………....(1mark)

III ………………………………………………………………………………….(1mark)

b) Write the equation leading to the formation of M and N (1mark)

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

c) State the type of reaction in step IV (1mark)

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d) Write down the name of the compound E (1mark)

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e) Give the name and structural formula of compound F (1mark)

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f) Write the equation leading to the formation of compound F (1mark)

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g) Give an economic importance of F (1mark)

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h) Name compound

i) W (1mark)

………………………………………………………………………………………………

ii) P (1mark)

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7. The flow chart below shows analysis of mixture ‘R’ that contains two salts

a) Study the analysis and answer the questions that follow.

(i) What condition is necessary for the process in step 1 to take place? (1mark)

……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

(ii) Draw a labeled diagram of the set up that could be used to separate the mixture formed in step II (2marks)

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(iii) Write an ionic equation for the reaction that produces a colourless solution when access aqueous ammonia is added to filtrate X (1mark)

……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

iv) What observation would indicate the presence of NO2(g) in step 1 (1mark)

b) (i) What conclusion can be drawn from step(IV) only? Explain (1mark)

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

(ii) Write the formula of an anion present in residue U. Explain (1mark)

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(iii) Suggest the identity of the cation present in solution Z (1mark)

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c) Name the two present in mixture R (1mark)

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